8. What happens when the kidneys stop working?

Question 1

What 4 things happen when the kidneys stop working?

Answer 1

Loss of excretory function (accumulation of waste)
Loss of homeostatic function (electrolyte balance, acid-base control, volume)
Loss of endocrine function (erythropoietin, 1-alpha-hydroxylase Vit D)
Abnormality of glucose homeostasis (Decreased gluconeogenesis)

Question 2

What causes the symptoms of lethargy and anorexia?

Answer 2

Accumulation of nitrogenous waste products 
Acidosis 
Hyponatremia 
Volume depletion 
Anaemia

Question 3

What could cause salt and water imbalance? (“Salt retentainers”)

Answer 3

Inability to excrete salt and water, leads to a tendency to retain Na+ (Causes Hypertension, Oedema and Pulmonary oedema)

Question 4

What could cause salt and water imbalance? (“Salt losers”)

Answer 4

Tubulointerstitial disorders in which the conc. mechanisms have been damaged
Inability to decrease Na+ excretion (i.e. increase Na+ reabsorption) when Na+ depleted.
Causes osmotic diuresis (as high conc. small MW waste substances, e.g., urea)

Question 5

What does an inappropriately high loss of salt result in?

Answer 5

Volume depletion

Low BP

Question 6

Signs and symptoms of renal failure

Answer 6

“Very unwell”
Pale, Hands cold 
Capillary refill decreased
Poor skin turgor
Low pulse rate 
Low BP
Tachypnoeic
Clear lungs on auscultation

Question 7

What in a blood test may indicate renal failure?

Answer 7

High plasma creatinine and urea

Question 8

Ultrasound findings in renal failure

Answer 8

Small, shrunken kidneys

Question 9

What is acidosis caused by?

Answer 9

Decreased excretion of H+ ions and retention of acid bases

Question 10

Why does acidosis tend to aggravate hyperkalaemia?

Answer 10

Excess H+ is buffered by taking it into cells in exchange for K+
So extracellular K+ concentration increases

Question 11

How can serum and total body sodium levels vary?

Answer 11

Can have low Na+ in blood, but excess total body Na+ if oedematous
Can have high Na+ in blood, but low total body Na+
Conc. not always aligned to total body levels

Question 12

What respiratory compensation mechanism is seen in response to metabolic acidosis?

Answer 12

Increasing CO2 loss through the lungs

Air hunger, rapid breathing

Question 13

What is a serious consequence of hyperkalaemia?

Answer 13

Can cause CARDIAC ARRHYTHMIAS

initial loss of p waves, bradycardia, arrest

Question 14

What can hyperkalaemia effect?

Answer 14

Neural and muscular activity

Question 15

What effect does renal failure have on the production of erythropoietin? What is the result of this?

Answer 15

Decreases erythropoietin production

Results in anaemia

Question 16

What effect does renal failure have on 1-25 Vitamin D levels? What is the result of this?

Answer 16

Decreases levels of 1-25 Vitamin D

Results in hypocalcaemia (short term) and hyperparathyroidism (long term)

Question 17

A major predictor of end stage renal failure is chronic kidney disease, but what is a major outcome for patients with chronic kidney disease?

Answer 17

Cardiovascular Disease

Question 18

What potential mechanisms cause CVD in patients with CKD?

Answer 18

Hypertension
Secondary cardia effects
Endothelial effects
Lipid abnormalities

Question 19

State 5 similarities between acute and chronic kidney disease.

Answer 19

Anaemia 
Acidosis 
Tendency to hyperkalaemia
Tendency to hyponatreamia 
Volume usually overloaded (Oedema)

Question 20

State 2 differences between acute and chronic kidney disease.

Answer 20

Acute: renal size unchanged + previously normal creatinine

Chronic = renal size DECREASED, previously ABNORMAL creatinine, chronic uraemia symptoms

Question 21

When might a patient with chronic kidney disease have normal sized kidneys?

Answer 21

Polycystic kidney disease
Diabetes
Myeloma
Amyloid

Question 22

What is the initial management plan for someone suffering from kidney disease?

Answer 22

IV saline to correct fluid loss
IV sodium bicarbonate to correct acidosis
IV insulin and dextrose to lower plasma K+ (increase uptake of K+ into cells)

Question 23

What are the methods of estimating GFR?

Answer 23

Urea (poor indicator: confounded by diet, drugs, liver function)
Creatinine (affected by muscle mass, age, race, sex) 
Creatinine Clearance (difficult in elderly patients to collect an accurate sample) 
Inulin Clearance (laborious) 
Radionuclide Studies (EDTA clearance, expensive)

Question 24

Estimated GFR (EGFR) equation

Answer 24

Equation accounts for creatinine, age and ethnicity

Still need to look at patient